Here's a link about that -> http://en.wikipedia.org/wiki/Native_resolution
I can't offer much else but try the exact resolution of the LCD next time.
When I link my Macbook Pro with my Dell U2410 I get a fuzzy picture. I have two Macbooks and two Dell U2410s, the problem is the same on both? Is this a common issue? Are there any solutions? Dell "support" is clueless about this. Apple tries to help, but is sure it is a compatibility issue between the MacBook and the Dell U2410.